Canvas sizing in Inkscape?

Can anyone explain how to set your canvas to a specific size and how to save your image when using textures. I did a background and after saving it, I noticed the texture didn't save(for whatever reasons unknown to me) but when I opened the .svg file back in Inkscape the textures was there. Any suggestions? Thanks in advance

He who knows nothing is closer to the truth than he whose mind is filled with falsehoods and errors.